Polyols or polyhydroxyl alcohols are chemical compounds which contain various oxyhydryl or hydroxyl groups (--OH) in their molecules. They are also known as polyalcohols and in an abbreviated form, precisely polyols.
These polyols are important in the industrial application of polyurethane foams and, depending on their particular characteristics, such as functionality, oxyhydryl number and molecular weight, find specific uses in the production of said foams to impart to the same flexibility, rigidity, elasticity, etc.
It is well known that in order to produce polyols industrially it is necessary to begin with an alcohol with a given group of oxyhydryls per mol. The alcohol is reacted with an alkylene oxide under certain conditions of catalysis, temperature, pressure and time. Further, in order to produce rigid polyurethane foams it is necessary to employ a polyol with a function greater than three. Therefore, the alcohols employed to produce a polyol must have a high function in order to admix and react with the alkylene oxides and obtain a functionality greater than three.
However, some of the most used alcohols having polyfunctions are solids at ambient temperature and inclusive at reaction temperatures (between 80 and 130 degrees C.). Trimethylolpropane, pentaerythritol, sorbitol, sucrose, etc. are some of the examples of these alcohols.
Upon requiring a greater function, it is necessary to employ materials such as sorbitol and sucrose. The temperatures of fusion of these materials are very high and normally close to their temperature of decomposition, all of which makes handling the materials difficult.
Since some time before, processes have been developed for obtaining polyether from polyols by reacting alkylene oxide with sucrose. The principal part of these processes is the handling of the sucrose during the process for obtaining the polyol.
Some processes are described in the literature involving the reaction of the sucrose with alkylene oxide in volume. This reaction has the advantage that products of high f unction (7-8) are obtained and that the reaction time is short. In this way the sucrose is suspended in the alkylene oxide. However, in this way polyols with high viscosity normally between 40,000 and 400,000 centipoises at ambient temperature, are obtained. This is not practical since problems are caused in the handling of the polyol in normal foaming machines. Also, there is a risk represented by handling large quantities of alkylene oxide within the reactors at the reaction temperature due to the high vapor pressure, which makes this highly explosive.
Other processes are also known, involving the use of inert solvents such as toluene, xylene or benzene which dissolve the sucrose and expedite the oxyalkylation thereof, thus reducing the yield due to the use of 10 to 40% of the solvent.
Also, other processes exist where the sucrose is diluted in alcohols which react at the same time with the alkylene oxides. One of the most common is water which upon reacting forms oxyalkyl compounds with a function of two and which are harmful to the production of rigid polyurethane. Some other alcohols used are monoethylene glycol, monopropylene glycol, triethanolamine, glycerine, ethylenediamine, etc.
In all the known processes alkylene oxides are used. Propylene oxide is the most common alkylene oxide used and only in a few processes is use made of ethylene oxide in amounts up to 40%.
U.S. Pat. No. 3,153,002 includes examples wherein the content of ethylene oxide amounts up to 65%, using water to dilute the sucrose and carrying out the reaction at a very low temperature, up to 43 degrees C.
U.S. Pat. No. 2,902,478 includes an example wherein the content of ethylene oxide amounts to 47%, the reaction being initiated in mass and at a pressure of 155 psig which evidently is very dangerous. Also a high viscosity is obtained, which is undesirable.
As is evident from the above, there is a need for a practical, effective and convenient product of low viscosity and high content of ethylene oxide which does not have the disadvantages of the products previously mentioned.